2c(2) states:

Array initializers can specify the indices of the array in
  square brackets, as
      int a[] = { [3] 1, [10] 5 };
  which initializes the third and tenth elements of the
  eleven-element array a.

This is somewhat confusing: the third and the tenth element should have index 2 and 9. Moreover if the tenth element is actually referred by index 10, why the array should hold eleven elements?

A simple check shows that actually the array has 11 elements and the one initialized are the forth and the eleventh.

Giacomo